Download Cellular Respiration

RECAP
• Photosynthesis produces:
– Oxygen
– Sugar (glucose)
– How will these substances be used to make
ATP for the organism?
Cellular Respiration
• Chemical bond energy in food molecules
is converted to a form that can be used by
the cell (ATP)
Energy stored in food is measured in calories
– Fats store more energy per gram than do
carbohydrates and proteins
Cellular Respiration may be:
• Anaerobic: doesn’t require oxygen
• Aerobic: requires oxygen
Anaerobic Respiration
• Makes a small amount of usable energy
without using oxygen
• Reactions occur in cytoplasm
• Produces 2 ATP per glucose molecule
• Takes place in yeast, and bacteria
• Can also occur in human muscle
cells if no oxygen is present.
Anaerobic Respiration
Glycolysis: (sugar is “split”)
Glucose is only partially broken down
Not all of it’s stored energy is released
C6H12O6 + 2 ATP → 2 pyruvic acid + 4 ATP
(6-carbon)
(3-carbon)
Needed to start
Net gain of energy is 2 ATP
Are produced
What Happens to Pyruvic Acid?
What happens to Pyruvic Acid?
• Fermentation of Alcohol
– (Oxygen not present)
C6H12O6 → Ethyl Alcohol + CO2 + 2ATP
– Happens in Yeast
– Pyruvic acid (from split glucose) is turned into
ethyl alcohol and CO2 (carbon dioxide)
– Useful in the brewing and baking industries
• Produces alcohol
• Produces carbonation
• Bubbles of CO2 make bread rise
What happens to Pyruvic Acid?
• Fermentation of Lactic Acid:
– (Oxygen not present)
C6H12O6 → Lactic Acid + 2ATP
– Happens in some bacteria
• Pyruvic acid (from split glucose) becomes lactic acid
• Used to make cheese, yogurt and buttermilk
GLYCOLYSIS
Alcohol Fermentation
Lactic Acid Fermentation
Let’s Try This
• Activity: Finger “Crunches”
– As fast as possible crunch your fingers 100 times
Lactic Acid buildup in human muscle cells
• During intense exercise, if oxygen is not present,
human muscle cells use anaerobic respiration to
produce some energy, yielding lactic acid
• Lactic acid builds up
• Muscles eventually cramp up (burning feeling)
Oxygen Debt:
• Eventually Lactic acid goes to your liver where it is
changed back into glucose which can be used again.
• In order to convert the lactic acid, your body needs oxygen
When You Die
Anaerobic Respiration
• Glycolysis happens in cytoplasm
• To produce more ATP, (if oxygen present)
reactions must take place in the Mitochondria
Mitochondria Structure
Aerobic Respiration
• Makes more ATP using oxygen
• Occurs in mitochondria
• Most eukaryotic organisms carry out
aerobic respiration
• Plants also carry out respiration!!!
• Glucose gets completely broken down to
release energy
• Releases more energy than anaerobic
respiration (more energy efficient)
• Most of the CO2 and H2O you exhale is
produced from aerobic respiration
C6H12O6 + O2 → CO2 + H2O + 36 ATP
Aerobic
Respiration
Summary
3 Steps of Aerobic Respiration
Step 1: Glycolysis
– Same as in anaerobic respiration
– Doesn’t require oxygen
– Takes place in cytoplasm
– Glucose is split producing 3-carbon pyruvic acid
• Also produces NADH from NAD+
• This “carries” some high energy electrons and H+
– Net production of 2 ATP
Step 2: Kreb’s Cycle (Citric Acid Cycle)
– Requires oxygen
– Pyruvic acid from glycolysis enters mitochondria
– Reactions occur in mitochondrial matrix
– Produces high energy electron/hydrogen carriers
• NADH and FADH2 (called coenzymes)
• These molecules carry “H+” and high energy electrons
• These will be used later to help produce more ATP
– Produces CO2 gas
– Produces 2 ATP
Aerobic
Respiration
Summary
Step 3: Electron Transport Chain
– Requires oxygen
– Occurs on inner membrane of mitochondria
– Uses high energy electrons and H+ to convert ADP
to ATP
• Uses the NADH/FADH2 from glycolysis & Krebs cycle
– Final electron & hydrogen acceptor is oxygen
(which then becomes H2O which is released)
– Produces 32 ATP!!!
– Produces H2O
• Animation of Electron Transport Chain
• Note that Oxygen is the final electron
acceptor and accepts 2 H+ to become
water!
• http://vcell.ndsu.nodak.edu/animations/etc/
movie-flash.htm
• Respiration Animation
• http://www.qcc.cuny.edu/BiologicalScience
s/Faculty/DMeyer/respiration.html
Anaerobic Phase
Doesn’t need O2
Aerobic Phase
Needs O2
Efficiency of Cellular Respiration
Anaerobic: Yields 2 ATP per glucose
– End products of fermentation still contain a lot of
unused potential energy
– Meets energy needs of simple organisms
Aerobic: Yields 36 ATP per glucose
– More efficient
– 45% of the energy available in glucose is transferred
to ATP where it can do further work for the cell
– Note: Car engines only converts about 25% of the
energy from gasoline
Respiration of Fats and Proteins
• Get broken down and converted into amino
acids, glycerol and fatty acids
• These can enter respiration pathway at
different points
– Fats yield twice as much ATP as glucose
– Proteins yield about the same as glucose but are
not the preferred energy source for the cell
Evolution of Cellular Respiration
• First life originated when there was hardly any
oxygen in the atmosphere.
(Probably prokaryotes with few organelles and no
mitochondria)
– Glycolysis was the first biochemical process to
evolve
– Happens in cytoplasm and no oxygen needed.
Comparing Photosynthesis and
Cellular Respiration
• How are these two processes related to
each other?
• In a typical plant cell describe the way
energy is obtained and utilized through
both photosynthetic and respiration
processes.
– Include the materials that need to be taken in
and released
Comparing
Photosynthesis and Respiration